Photographic process comprising improved dye bleaching step



United States Patent Int. Cl. G03c 5/38 US. CI. 96-53 19 Claims ABSTRACT OF THE DISCLOSURE An improved photographic process comprising an improved and rapid dye bleaching step comprises: (1) exposing to an image pattern of activating radiation a dyesensitized photosensitive copy medium which becomes activated at portions thereof which are exposed to such activating radiation and, (2) applying to the exposed medium a dye bleaching solution of a solvent soluble thionate selected from at least one of the group of sulfites and bisulfites and especially those of Groups I-A and II-A metals, said thionate having a concentration of at least about 0.1 mole of thionate per liter of solution; an amide, said amide having a concentration of from about 0.5 to 15.0 moles of amide per liter of solution; and optionally an ether, said ether having a concentration of from about 0 to 2.0 moles of ether per liter of solution. This dye bleaching solution can be applied to the photosensitive copy medium along with the imageforming material, stabilizing bath, fixing bath, stop bath, or washing-aid bath. In a preferred embodiment, the dye bleaching solution is combined with the stabilizing or fixing bath. In such an embodiment wherein the thionate in potassium sulfite and the stabilizing or fixing bath is an aqueous solution of sodium thiosulfate, the potassium sulfite serves the dual function of a bleaching agent for a colored dye-sensitive copy medium and also a preservative for the sodium thiosulfate.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to the field of photographic reproduction systems, and, more specifically, to a photographic system utilizing an improved copy medium comprising a photosensitive material sensitized with a bleachable dye, which photosensitive material when activated by suitable means, is capable of producing a visible image.

Description of the prior art Data or image storage media comprising radiationsensitive materials such as titanium dioxide are described in detail in US. Pats. 3,152,903; 3,152,904; 3,052,541; French Pats. 345,206 and 1,245,215 and in commonlyowned co-pending US. application Ser. No. 199,211, filed May 14, 1962 and now abandoned in the names of Elliot Berman et al. In the aforementioned US. Patent application, radiation-sensitive titanium dioxide functions as a photosensitive component of the media and exposure of said media to activating means such as radiant energy, electron beams or the like results in the storage of a reversible latent image pattern therein. The reversible latent image pattern exists for a limited time during which said pattern can be converted to an irreversible form and read out visually by contacting said pattern with a suitable image forming material, such as a chemical redox system. In the aforesaid US. and French Patents, the radiation-sensitive material is combined with at least one component of an image-forming material prior to exposure to activating means. For example, US. Pat. 3,- 152,904 describes a photosensitive copy media comprising a photosensitive material such as titanium dioxide in combination with a reducible metal ion such as silver "ice nitrate. This copy media is exposed to activating means to produce a visible image. On the other hand, US. Pat. 3,152,903 discloses a system wherein the photosensitive material is used in combination with both an oxidizing agent such as silver nitrate and a reducing agent such as hydroquinone. Upon exposure to suitable activating means, a visible image is formed.

One of the features of the above-mentioned data or image storage systems is that the photosensitive materials are often sensitive to a very narrow range of electromagnetic radiation. Therefore, it is often desirable to sensitize these photosensitive materials to additional ranges of electromagnetic radiation by application of dyes. Such dyes are well known to the art and include, for example, cyanine dyes, dicarbocyanine dyes, the carbocyanine dyes, and the hemicyanine dyes. Such dye-sensitized systems are disclosed in co-pending application U.S. Ser. No. 432,887 filed Feb. 15, 1965 and now abandoned, in the names of E. Berman et al., co-pending application U.S Ser. No. 359,956 filed Apr. 15, 1964 in the names of R. F. Bartlett et al., now US. Pat. No. 3,414,410, and copending application U.S. Ser. No. 633,689 filed Apr. 26, 1967 in the names of J. H. H. Keller and R. S. Sprague.

One of the problems with using such dyes to sensitize the photosensitive medium is the removal of the dye after development of the latent image to a visible image in order to obtain a final print with a white background. In the past this dye removal has been accomplished by dissolving the dye out of the substrate or by contacting with a suitable oxidizing agent. However, these methods have either been extremely slow or the oxidizing agent has been so strong that it produced detrimental effects upon the visible image formed in the final print. Copending application U.S. Ser. No. 641,126 filed May 25, 1967 in the names of R. C. Beach et al. entitled Photographic Process Comprising Dye Bleaching Step teaches that a dye which has been incorporated in a photosensitive medium can "be bleached by a solution of a solventsoluble thionate selected from at least one of the group of sulfites and bisulfites wherein the concentration of the thionate is at least about 0.5 mole per liter of solution. However, one of the serious limitations of this process and dye bleaching solution is that the dye is generally incompletely bleached or if complete bleaching is achieved, it is only after a very prolonged period of time.

SUMMARY OF THE INVENTION It has now been unexpectedly found that a photosensitive medium sensitized with a bleachable dye in the colored form may be rapidly converted to the colorless state without detrimental effects to the final print when contacted with an improved dye-bleaching solution of (l) a solvent-soluble thionate selected from at least one of the group of the sulfites and bisulfites and especially those thionates of the metals of Groups I-A and II-A of the Periodic Table, preferably having a concentration of from about 0.1 moles of thionate per liter of solution to a solution being saturated with the thionate, (2) an amide in which the dye being bleached is soluble, said amide having a concentration of from 0.5 to 15.0 moles of amide per liter of solution, and optionally (3) an ether in which the dye being bleached is at least partially soluble, said ether having a concentration of from 0 to 2.0 moles of ether per liter of solution. More particularly, this invention involved a process for recording an image pattern of activating radiation compris ing exposing to an image pattern of activating radiation a photosensitive copy medium sensitized with a bleachable colored dye which becomes activated at portions thereof which are exposed to activating radiation, wherein 1 Periodic Table from Langes Handbook of Chemistry, 9th edition, pp. 56-57.

the improvement comprises applying to the exposed copy medium an improved dye bleaching solution as above described. In a preferred process, the thionate is incorporated in image-forming material, in stabilizing bath, in fixing bath, or in stop bath which is applied to an exposed and developed photosensitive copy medium. There fore, a preferred embodiment comprises a photosensitive copy medium sensitized with a bleachable dye which is exposed to an image pattern of activating radiation, then contacted with an oxidizing agent such as a solution of silver nitrate, then contacted with a solution of a reducing agent such as Metol, and finally contacted with a combined stabilizing bath and dye-bleaching solution comprising, for example, sodium or ammonium thiosulfate, potassium sulfite, an amide and an ether, either of which amide and ether are capable of dissolving, at least partially, the dye which is being bleached.

A preferred process comprises a heating step subsequent to the step of contacting the dye-sensitized copy medium with the dye-bleaching composition of this invention. Heat acts to further accelerate the dye-bleaching process.

DESCRIPTION OF PREFERRED EMBODIMENT The thionates of the improved dye-bleaching solution of this invention are preferably selected from at least one of the solvent soluble sulfites and bisulfites and more especially those of Groups I-A and II-A metals. Potassium sulfite and bisulfite are especially preferred because of their increased solubility in an aqueous solution. Any solvent which does not significantly interfere with the reaction may be used in the improved dyebleaching composition of this invention. Polar solvents are generally preferred. Water is especially preferred as a solvent because of its economy.

The thionates of this invention may be incorporated in any of the image-forming materials or in the stabilizing bath. The stabilizing bath used to fix or stabilize the developed print are those fixing or stabilizing baths such as described in the silver halide photographic arts, such as potassium thiocyanate solution, sodium thiosulfate solution, or solutions of other sulfur compounds. Suitably, the fixing or stabilizing baths contain a material which complexes excess metal ion which may be present on the developed and amplified image areas as well as the non-image areas, and prevents its further deposition as free metal. When silver ion is present, for example, water soluble thiosulfates such as potassium thiosulfate or sodium thiosulfate are usually used as complexing agents in the fixing bath.

The amides useful in the improved dye bleaching solution of this invention are those in which the dye being bleached is at least partially soluble. Suitable amides are those of the general formula wherein R, R and R may be the same or difierent, and may be any of hydrogen, alkyl, aryl, aralkyl, and alkaryl groups, wherein R or R may be an group, and wherein R and R may form part of the same ring structure, thus forming a substituted or unsubstituted cycloalkylene or aryl structure. Preferred amides are those wherein R, R or R are hydrogen or groups containing 10 or less carbon atoms. Exemplary of the amides which are useful in this invention are the following: formamide, acetamide, dimethyl formamide, dimethyl acetamide, benzamide, stearamide, and the higher amides such as diacetamide, (CH CO) NH, and triacetamide,

Suitable ethers which can optionally be added to the improved dye-bleaching solutions of this invention are those of the formula R OR wherein R and R may be the same or different and represent hydrocarbon groups such as alkyl, alkaryl, aryl and aralkyl groups. These hydrocarbon groups may be aliphatic, unsaturated, or aromatic, and their hydrogens may be replaced by other groups such as halogens or hydroxyl groups, e.g. 1- methoxy-2,3-propanediol. The ether group may also be present in ring compounds, such as dioxane. R and R may also represent ether groups themselves as for example in bis(Z-methoxyethyl) ether. Examples of some suitable ethers, useful in this invention, are diethyl ether, methyl ether, (bis(2-chloroethyl) ether, isopropyl ether, Cellosolve, diphenyl ether, bis(Z-chloroisopropyl) ether, n-butyl ether, amyl ether, n-hexyl ether, bis(Z-methoxyethyl) ether, and benzyl ether.

The photoconductor or photocatalyst preferred in this invention are metal containing photoconductors. A preferred group of such photosensitive materials are the inorganic materials such as compounds of a metal and a non-metallic element of Group VI-A of the Periodic Table such as oxides, such as zinc oxide, titanium dioxide, zirconium dioxide, germanium dioxide, indium trioxide; metal sulfides such as cadmium sulfide (CdS) zinc sulfide (ZnS) and tin disulfide (SnS metal selenides such as cadminum selenide (CdSe). Metal oxides are especially preferred photoconductors of this group. Titanium dioxide is a preferred metal oxide because of its unexpectedly good results. Titanium dioxide having an average particle size less than about 250 millimicrons and which has been treated in an oxidizing atmosphere at a temperature between about 200 C. and 950 C. for from about 0.5 hour to about 30 hours is especially preferred, and more especially that titanium dioxide produced by high temperature pyrolysis of titanium halide.

Also useful in this invention as photoconductors are certain fiuoroescent materials. Such materials include, for example, compounds such as silver activated zinc sulfide, zinc activated zinc oxide, manganese activated zinc phosphate Zn (PO an admixture of copper sulfide, antimony sulfide (SbS) and magnesium oxide (MgO), and cadmium borate.

While the exact mechanism by which the photoconductors of this invention work is not known, it is believed that exposure of photoconductors or photocatalysts of this invention to activating means causes an electron or electrons to be transferred from thevalence band of the photoconductor or photocatalyst to the conductance band of the same or at least some similar excited state whereby the electron is loosely held, thereby changing the photoconductor from an inactive form to an active form. If the active form of the photoconductor or photocatalyst is in the presence of an electron accepting com ound a transfer of electrons will take place between the photographic and the electron accepting compound, thereby reducing the electron accepting compound. Therefore a simple test which may be used to determine whether or not materials have a photoconductor or photocatalyst effect is to mix the material in question with an aqueous solution of silver nitrate. Little, if any, reaction should take place in the absence of light. The mixture is then subjected to light. At the same time that a control sample of an aqueous solution of silver nitrate alone is subjected to light, such as ultraviolet light. If the mixture darkens faster than the silver nitrate alone, that material is a photoconductor or photocatalyst.

It is evident that the gap between the valence and the conducting band of a compound determines the energy needed to make electron transitions. The more energy needed, the higher the frequency to which ahe photoconductor will respond. It is known to the art that it is possible to reduce the band-gap for these compounds by adding a foreign compound as an activator which either by virtue of its atomic dimensions or by possessing a particular electronic forbidden zone structure or through the presence of traps as donor levels in the intermediate zone between the valence and the conduction band stresses the electronic configuration of the photoconductive compound, thereby reducing its band-gap and thus increasing its ability to release electrons to its conduction band. Phosphors almost necessarily imply the presence of such activating substances. The effect of such impurities may be such as to confer photoconductivity upon a compound which intrinsically is non-photoconductive. The (Cr-Sr)S phosphors are believed to be an example of this group. On the other hand, excessive impurity content can interfere with a compound acting as a photoconductor, as above described.

Bleachable dyes useful for sensitizing the photosensitive copy medium of this invention include, for example, the cyanine dyes, the dicarbocyanine dyes, the carbocyanine dyes, and the hemicyanine dyes. Suitable cyanine dyes are the following: 3,3'-diethyl-4,5,4,5'-dibenzothiacyanine chloride; 3-B-carboxyethyl-1'-ethyl 6 methoxy-S-phenyl-thia-2'-cyanine iodide; 3,3'-diethyl-4,5,4',5-dibenzoxacyanine iodide; 3,3'-diethylthiazolinocarbocyanine iodide; 3,3'-diethyloxacarbocyanine iodide; and 3,3'-diethyl-9- methyloxaselenacarbocyanine iodide.

Suitable dicar-bocyanine dyes are the folowing: 3,3'-difl-hydroxyethylthiadicarbocyanine bromide; Anhydro-3,3'- di-[i-carboxyethylthiadicarbocyanine hydroxide; 3,3-diethyloxathiadicarbocyanine iodide; 3,3'-diethyl-4,5,4,5'- dibenzothiadicarbocyanine iodide; 3'-carboxymethyl-3- ethyloxathiadicarbocyanine iodide; 3-carboxymethyl-3'- ethyloxathiadicarbocyanine iodide; and 3,3'-di(carboxymethyl)oxathiadicarbocyanine bromide.

Suitable carbocyanine dyes are the following: 3,3-diethyl-9-methyl 4,5,4',5 dibenzothiacarbocyanine chloride; Anhydro-3,3-di fi carboxyethyl-S,5'-dichloro-9- ethylthiacarbocyanine hydroxide; anhydro-3-B-carboxyethyl-5,5'-dichloro 9 ethyl-3-fl-sulfoethylthiacarbocyanine hydroxide; 9-ethyl-3,3-di ,8 hydroxyethylthiacarbocyanine iodide.

Suitable hemicyanine dyes are the following: 2-p-dimethylaminostyryl-4-methylthiazole methochloride; 2-[4- (p-dimethylaminophenyl)-l,3-butadienyl] 1,3,3 trimethylpseudoindolium chloride; Z-(p-dimethylaminostyryl)- benzimidazole methochloride; 2-(p-dimethylaminostyryl)- 6-ethoxyquinoline methochloride; 6-dimethylamino-2- (p-dimethylaminostyryl)-quinoline methochloride; 2-p-dimethylaminophenyl 6 methylbenzothiazole methochloride (Thioflavine T); 3,3-dimethyl-2[6(p-dimethylaminophenyl) 1,3,5-hexatrienyl] indolenine ethiodide; 2(p-dimethylaminostyryl)-3,S-dimethylthiadiazolium nitrate; 2- p dimethylaminostyryl 4 methylthiazole-B-hydroxyetho-chloride; and Z-p-dimethylaminostyryl methyl- 1,3,4-thiadiazole-B-hydroxy-etho-chloride.

Aminostyryl hemicyanine dyes are an especially preferred class of dyes because of the improved photographic exposure speed and improved image densities for a given speed achieved with photosensitive copy media so sensitized.

Additional dyes which are useful for sensitizing the photosensitive medium of this invention are the cyanine dyes described on pp. 371-429 in The Theory of Photographic Process by C. E. Kenneth Mees published by McMillan Company in 1952. Other useful dyes include those known to the art as triphenylmethane dyes such as crystal violet and basic Fuchsin, diphenylmethane dyes such as Auroamine O, and Xanthene dyes such as Rhodamine B.

The dyes useful in this invention may be used in solution to treat the photosensitive materials prior to their incorporation into a copy medium. These dyed photosensitive materials can then be deposited on a substrate, or incorpo rated into a substrate such as a fibrous web of paper. Alter natively, the dye can be combined with the photoconductive materials in the copy medium as per example, by dispersion of the dye in the binder for the photosensitive 6 material. In addition, it is possible to dip dye the photosensitive substrate by merely immersing a substrate containing the photosensitive material into a solution of the particular dye.

Irradiation sources which are useful in this invention include any activating electromagnetic radiation. Thus actinic light, X-rays, or gamma rays are effective in exciting the photo-catalysts. Beams of electrons and other like particles may also be used in the place of the ordinary forms of electromagnetic radiation for forming an image according to this invention. These various activating means are designated by the term activating radiation.

The inert carrier sheet upon which the photoconductor and dyes of this invention are deposited comprises any suitable backing of sufficient strength and durability to satisfactorily serve as a reproduction carrier. The carrier sheet may be in any form such as, for example, sheets, ribbons, rolls, etc. This sheet may be made of any suitable materials such as wood, rag content paper, pulp paper, plastics such as, for example, polyethylene terephthalate (Mylar) and cellulose-acetate, cloth, metallic foil and glass. The preferred form of the carrier sheet is a thin sheet which is flexible and durable.

It is also useful to use a binder agent to bind the bleachable dye useful in this invention and photosensitive materials to the carrier sheet. In general, these binders are translucent or transparent so as not to interfere with transmission of light therethrough. Preferred binder materials are hydrophilic or hydrophobic organic materials such as resins. Examples of suitable resins are butadienestyrene copolymer, poly(alkyl acrylates) such as poly- (methyl methacrylate) polyamides, polyvinyl acetate, polyvinyl alcohol and polyvinylpyrrolidone.

The photoconductor should be conditioned in the dark before exposure. Such conditioning is generally conducted from one to twenty-four hours. After conditioning, the photoconductor is not exposed to light prior to its exposure to activating radiation for recording an image pattern.

The period of exposure will depend upon the intensity of the light source, particular photoconductor, the type and amount of catalyst, if any, and like factors known to the art. In general, however, the exposure may vary from about 0.001 second to several minutes.

Image-forming materials which are useful in this invention are those such as described in U.S. Pat. 3,152,903 and in co-pending application Ser. No. 199,211. These image-forming materials include preferably an oxidizing agent and a reducing agent. Such image-forming materials are often referred to in the art as physical developers. The oxidizing agent is generally the image-forming component of the image-forming material. However, this is not necessarily true. Either organic or inorganic oxidizing agents may be employed as the oxidizing component of the image-forming material. Preferred oxidizing agents comprise the reducible metal ions having at least the oxidizing power of cupric ion and include such metal ions as Ag+, Hg, Pb+ Au+ All Pt+ Pt, Ni+ Sn, Pb+ Cu, and Cu. Other suitable oxidizing agents useful in this invention as components of an imageforming material are permanganate (MnO ion, various leuco dye materials such as disclosed in co-pending application Ser. N0. 623,534 filed Mar. 19, 1967 in the name of L. Case, and the like. Organic oxidizing agents include tetrazolium salts, such as tetrazolium blue and red, and diphenyl carbonzone, and genarcyl red 63 (methine dye).

The reduction agent component of the image-forming materials of this invention are inorganic compounds such as the oxalates, formates, and ethylenediaminetetraacetate complexes of metals having variable valence; and organic compounds such as dihydroxybenzenes, aminophenols, and aminoanilines. Also, polyvinylpyrrolidone, hydrazine, and ascorbic acid may be used as reducing agents in this invention. Suitable specific reducing compounds include hydroquinone or derivatives thereof, oand p-aminophenol, p-methylaminophenol sulfate, p-hydroxyphenyl glycine, oand p-phenylenediamine, 1-phenyl-3-pyrazolidone, alkali and alkaline earth metal oxalates and as in Example 1 except that the combined dye-bleaching and fixing-stabilization bath is of the composition shown in Table I below. The optical density of the copy medium is measured seven (7) minutes after contacting the copy formates. medium with the bleaching solution.

TABLE I Example No.

2 3 4 5 6 7 s 9 10 58353.1 ifii itiiiifiisrjij13:31:: 538 $38 Acetic acid (mls) Fonnamide (moles) Dimethyl formamide (moles Acetamide (moles) Dimethyl acetamide (moles) Optical density 1 Weights are per liter of aqueous solution.

Additionally, the image-forming materials or physical developers may contain organic acids or alkali metal salts thereof, which can react with metal ions to form complex metal anions. Further, the developers may contain other complexing agents and the like to improve image formation and other properties found to be desirable in this art.

The invention above described is exemplified as follows:

EXAMPLE 1 A photosensitive copy medium comprising a paper support coated with a finely-divided titanium dioxide dispersed in a polyvinyl alcohol binder which has been dyesensitized with 2-p-dimethylaminostyryl-4-methyl thiazole methochloride is exposed to an image pattern from a tungsten light source for 1-2 seconds duration, thereby giving an exposure of 400 meter candle seconds.

The thus-exposed copy medium is then immersed 0.28 seconds in an aqueous solution of 0.32 molar silver nitrate then immersed 0.6 second in an aqueous developing solution comprising Metol (p-methylaminophenol sulfate), then immersed in a combined dye-bleaching and fixer-stabilizer bath of the following composition for 1 second:

Potassium sulfite (K SO )-200 grams Sodium thiosulfate (Na S O .5H O)-200 grams Glacial acetic acid-23 milliliters Dilute to 1 liter with water.

The copy medium is then allowed to sit for seven minutes and then tested on a MacBeth densitometer read through a blue filter to determine the completeness of bleaching. The densitometer reading gives a relative measure of the completeness of bleaching. The more complete the bleaching, the lower the optical density will be. After seven minutes the above-tested copy medium was substantially completely bleached, being converted from a bright orange to white in the non-image areas of the copy medium. The image areas of the copy medium were not adversely affected by the bleaching process. Seven minutes after removal of the copy medium from the bleaching-fixer bath, the densitometer reading of the above-mentioned copy medium was 0.15.

When 1.1 moles of acetamide is added to the above solution and a copy medium is otherwise exposed and processed in the manner above described gives an optical density on the MacBeth densitometer of 0.11 seven minutes after removal of the copy medium from the bleach-fixed bath. Thus it can be seen that the addition of an amide to a sulfite bleaching solution increases markedly the conversion of the colored dye to the colorless state. The color in the final print is decreased by 27% by the addition of the acetamide to the potassium sulfite bleach-fixer bath mentioned above.

EXAMPLES 2 1 0 A dye-sensitized TiO -coated copy medium of the composition described in Example 1 is exposed and treated EXAMPLES l 1-14 TABLE II Example No. 11 12 13 ii Acetamide (moles) 1 2. 5 1. 7 1. 2 1. 7 Sodium thiosulfate (NazSzOg) (grams) 50 Sodium sulfite (NazSOa) (grams) Potassium sulfite (KzSOa) (grams) 200 1 Weights are per liter of aqueous solution.

The orange background of the dye-sensitized copy medium is turned brown and no bleaching occurred after contacting this copy medium with the bleaching solution of Example 11. The bleaching solution of Example 12 had no effect on the orange color of a similar medium. The bleaching solution of Example 13 caused substantially complete bleaching of the orange dye in about five minutes after removal of the copy medium from the dye bleaching solution. The bleaching solution of Example 14 caused substantially complete bleaching almost immediately (within one (1) minute) after removal of the copy medium from the bleaching solution.

Examples 13 and 14 are modified by applying a fixing bath of potassium thiosulfate immediately prior to the application of the respective dye-bleaching solutions. The results of applying the dye-bleaching solutions to these thus-modified processes are substantially the same as those for Examples 13 and 14 as described above.

EXAMPLE 15 A dye-sensitized TiO -coated copy medium is prepared by dispersing a finely-divided titanium dioxide pigment in a polyvinyl alcohol binder and coating this composition on a paper substrate. This copy medium is then dyesensitized by a solution of 2-[4-(p-dimethylaminophenyl) 1,3-butadienyl]-1,3,3-trimethylpseudo-indolium chloride. The thus dye-sensitized copy medium was a bright blue color. This copy medium was then immersed in a combined dye-bleaching and fixing-stabilization bath of the following composition:

Potassium sulfite grams Sodium thiosulfategrams Formamide300 milliliters Aminobenzoic Acid-15 grams Water was added to make 1 liter of solution.

Within a few minutes after removing the copy medium from the bath, it has turned from a bright blue color to a substantially white and fully-bleached condition. A combined dye-bleaching and fixing-stabilization bath of the same composition as described above except that the formamide is not present gives incomplete bleaching when a dye-sensitized substrate as described above is immersed in such a bath. Thus the presence of formamide not only accelerates the bleaching process but also makes possible a more complete bleaching.

EXAMPLE 16 A dye-sensitized TiO -coated copy medium of the com position described in Example 1 is exposed and treated as per the procedure of Example 1 except that the combined dye-bleaching and fixing-stabilization bath is of the following composition:

Potassium sulfitel grams Sodium thiosulfatel00 grams Formamide--3.9 moles Bis(2-methoxy ethyl) ether--l.0 mole l-methoxy-2,3-propanediol1.2 moles Water is then added to make up 1 liter of solution. The optical density of the background areas of the thustreated copy medium is .11 at the end of seven (7) minutes after removing from the bleach-fixer solution.

EXAMPLE 17 A dye-sensitized TiO -coated copy medium of the composition described in Example 1 is exposed and treated as per the procedure of Example 1 except that the combined dye-bleaching and fixing-stabilization bath is of the following composition:

Potassium sulfite-100 grams Sodium thiosulfatel00 grams Formamide-5.5 moles Bis (2-methoxy ethyl) ether.8 mole Water is then added to make up 1 liter of solution. The optical density of the background areas of the thus-treated copy medium is .10 at the end of seven (7) minutes after removing from the bleach-fixer solution.

EXAMPLE 18 A dye-sensitized TiO -coated medium of the composition described in Example 1 is exposed and treated as per the procedure of Example 1 except that the combined dye-bleaching and fixing-stabilization bath is of the following composition:

Potassium sulfite100 grams Sodium thiosulfate-lSO grams Formamide9.0 moles Water is added to make 1 liter of solution. Within about 75-90 seconds after removing the copy medium from this bleach-fixer bath, the orange-colored background areas of the copy medium appear to be completely bleached.

In the claims:

1. In a process for recording an image pattern of activating radiation comprising exposing to an image pattern of activating radiation a dye-sensitized photosensitive copy medium which becomes activated at portions thereof which are exposed to activating radiation, the improvement comprising applying to said medium at a point in time subsequent to the exposing step a solution of (1) a thionate selected from at least one of the group of the solvent-soluble sulfites and bisulfites, (2) an amide in which the dye of the dye-sensitized copy medium is at least partially soluble, and optionally (3) an ether in which the dye of the dye-sensitized copy medium is at least partially soluble.

2. A process as in claim 1 wherein the thionate is a thionate of the Group I-A and Group II-A metals.

3. A process as in claim 2 wherein the thionate is at least one of the group of sodium thionate and potassium thionate.

4. A process as in claim 1 wherein the solution is an aqueous solution.

5. A process as in claim 1 wherein the amide is at least one of the group selected from formamide, acetamide, dimethyl formamide, and dimethyl acetamide.

6. A process as in claim 1 wherein the ether is a his (alkoxyalkyl) ether.

7. A process as in claim 1 wherein the dye used to dyesensitize the photosensitive copy medium is at least one of the group selected from (1) cyanine dyes, (2) dicarbocyanine dyes, (3) carbocyanine dyes, and (4) hemicyanine dyes.

8. A process as in claim 7 which comprises an additional heating of the copy medium in order to accelerate the bleaching.

9. A process as in claim 7 wherein the dye-sensitizing composition is Z-p-dimethylaminostyryl-4-methylthiazole methochloride.

10. A process as in claim 7 wherein the dye-sensitizing composition is Z-p-dimethylaminostyryl-3,5-dimethyl-thiadiazolium nitrate.

11. In a process for recording an image pattern of activating radiation comprising exposing to an image pattern of activating radiation a photosensitive copy medium which has been sensitized by a dye selected from at least one of the group comprising (1) cyanine dyes, (2) dicarbocyanine dyes, (3) carbocyanine dyes, and (4) hemicyanine dyes, which becomes activated at portions thereof which are exposed to activating radiation, contacting said exposed medium with an image-forming material to produce a visible image and then fixing said visible image by contacting the medium with a fixing bath, the improvement comprising applying to said medium at a point in time subsequent to the exposing step, a dye-bleaching solution of 1) a thionate selected from at least one of the group of solvent-soluble sulfites and bisulfites having a concentration of at least about 0.5 mole of thionate per liter of solution, (2) an amide in which the dye of the dye-sensitized copy medium is at least partially soluble, said amide having a concentration of from about 0.5 to 15.0 moles of amide per liter of solution, and optionally (3) an ether in which the dye of the dye-sensitized copy medium is at least partially soluble, said ether having a concentration of from 0 to about 2.0 moles of ether per liter of solution.

12. A process as in claim 11 wherein the sulfites and bisulfites are those of the Group IA and Group IIA metals.

13. A process as in claim 12 wherein the photosensitive copy medium comprises titanium dioxide.

14. A process as in claim 11 wherein the dye-bleaching solution is combined with a stabilizing bath.

15. A process as in claim 14 wherein the sulfite is potassium sulfite and the stabilizing bath comprises a thiosulfate solution.

16. A process as in claim 15 wherein the solution is an aqueous solution.

17. A process as in claim 11 which comprises the additional step of heating the copy medium.

18. A process as in claim '11 wherein said amide is selected from at least one of the group of formamide, acetamide, dimethyl formamide, and dimethyl acetamide.

19. A process as in claim 11 wherein said ether is his (Z-methoxy ethyl) ether.

NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner US. Cl. X.R. 

